Miljacka cave spring

There are five known cave-springs (Miljacka I, II, III, IV and V). The largest, Miljacka II, is also the largest within the park bounds, and is situated on the right bank of the river, just a hundred metres downstream from the waterfall.

During periods of high water, a subterranean river flows through the cave, thought to be water from the Zrmanje River that sinks at Mokro Polje. During periods of low water, the cave contains a 200 m long lake of unknown depth, ending in a siphon. The cave has been investigated to a length of 1,750 m. The ceiling, floor and walls of the cave are ornamented with numerous eroded stalagmites, which indicate the frequent changes in water levels in the cave. The caves around Miljacka slap are exceptional underground habitats, with 36 subterranean species recorded to date, the majority of which are endemic to Croatia and/or the Dinaric karst area.

The Miljacka II cave is a known habitat for the endemic olm (Proteus anguinus) and 8 species of bats. During the summer bats, bat colonies with up to 9,000 individuals take shelter here, the most abundant of which is the long-fingered bat (Myotis capaccinii) with about 7,000 individuals.